1. Field of the Invention
This invention relates to a marking apparatus and a marking method; more particularly, to an optical marking apparatus and a method for applying a light beam to an object, to form a mark thereon.
2. Description of the Related Art
Laser marking is essentially a technique of marking on a given product the name of the manufacturer and a serial number, by means of a laser beam, so as to render the product readily identifiable.
There are two main methods of forming marks by laser marking. One method, used in the case of relatively complicated patterns, such as a company emblem or Chinese characters, is to raster-scan the mask of a pattern to be formed on an object or work by means of a laser beam, and then to project a light beam having a cross section corresponding to the pattern onto the object surface. The other method, used in the case of simple designs, such as serial numbers, is to scan a laser beam in a single stroke, without using a mask, and thus directly mark the object.
In the case of the marking technique using a mask, a desired pattern can be formed in advance on a mask by, for example, etching and thus a relatively complicated pattern can be marked easily and precisely. However, in the case where simple designs ar intended to be marked, this method has a problem in that it requires changing masks every time a new pattern is intended to be marked. This renders the operation of the system undesirably complicated.
In the case of the technique of applying a laser beam directly to the object, a pattern can be marked by the laser beam being moved by CPU control in accordance with the pattern to be formed. However, the more complicated the pattern to be formed, the more complicated the movement of the light beam is likely to be, thus necessitating ever more complex programming for controlling the movement of the light beam.
Moreover, employing the direct beam application method has a limitation in that the shape of a pattern marked is defined by the spot shape of the laser beam as well as the spot diameter. In other words, if a laser beam having a large spot is used, the edge portion of the pattern marked may be rounded rather than sharply defined.